Preparation and characterization of antibacterial poly(lactic acid) nanocomposites with N-halamine modified silica.

In this work, silica nanoparticles modified with a new N-halamine precursor (EBDMH-SiO2 NPs) were synthesized through immobilization of 3-(4'-epoxyethyl-benzyl)-5,5-dimethylhydantoin (EBDMH) on the surface of amino-functionalized silica NPs. Then, EBDMH-SiO2 NPs and poly(lactic acid) (PLA) were blended at 185 °C to prepare a novel environmentally friendly PLA based nanocomposite (PLA/EBDMH-SiO2). The addition of EBDMH-SiO2 NPs has great influences on the thermal properties of nanocomposite. DSC results show that the grass transition temperature (Tg), cold crystallization temperature (Tcc) and melting temperature (Tm) of PLA in nanocomposites gradually decrease with the increase of EBDMH-SiO2 NPs contents up to 5%. After that, further rise in EBDMH-SiO2 NPs content actually increases Tg, Tcc, and Tm. The overall crystallization and spherulite growth rate of PLA show the similar trend. Furthermore, the introduction of EBDMH-SiO2 NPs increases the storage modulus and viscosity of the melt of nanocomposite, providing an additional benefit for PLA blowing and injection molding. After chlorination, the N-halamine precursors on the nanocomposite surfaces are transformed into N-halamines, which provide strong antibacterial activities against E. coli (CMCC 44103) and S. aureus (ATCC 6538), pointing to good potentials of the PLA/EBDMH-SiO2 nanocomposites for antibacterial applications including food packaging, filters, and a wide range of hygienic products.